Currently daggers can only be transmogged into daggers, and only daggers can be transmogrified into daggers (yes, those are different statements! :P). Similarly, fists can only be transmogged into fists, and only fists can be transmogged into fists.

They are only allowing for weps of similiar animation (swing animations) to be mogged into one another. So in other words, daggers are only mog-able into daggers and you can't mog 1h weps into fist weps.